Void Jellyfish

Alien Nature. The Void Jellyfish's spells do not count as spells for the purpose of an Antimagic Field, Detect Magic, Counterspell, Dispel Magic, or similar effects that work specifically for spells and magical effects. 

Antimagic Dampener. The Void Jellyfish has advantage on saving throws against spells and other magical effects. Upon a failed saving throw, the Void Jellyfish only takes half damage. On a successful saving throw, the Void Jellyfish takes no damage and redirects the spell back to the caster. 

Cryptic Nature. The Void Jellyfish is immune to the effects of Divination spells. The Void Jellyfish leaves no tracks or scent for creatures to follow unless it chooses to. 

Displacement Field. The Void Jellyfish projects a magical illusion that makes its appearance hard to decipher. Attack rolls against it have disadvantage. 

Immutable Form. The Void Jellyfish is immune to any spell or effect that would alter its form unless it wishes to be affected by it. 

Unusual Appearance. The Void Jellyfish doesn't need to breathe, eat, or sleep.

Innate Spellcasting. The Void Jellyfish's innate spellcasting ability is Charisma(spell save DC 17). The Void Jellyfish can innately cast the following spells, requiring no material components:

• At will: Arcane Gate, Dancing Lights, Dimension Door, Invisibility, Legend Lore, Plane Shift(self only), Scrying, Reverse Gravity, Teleport(self only). 

Plasma Beam. Creatures in a 120ft long cylinder with a 10ft radius originating from under the Void Jellyfish must succeed on a DC 17 Dexterity saving throw or take 18(4d8) radiant damage plus 18(4d8) force damage. If a creature is reduced to 0 hit points by this attack, it is disintegrated and turns to ash, only being revived by a wish spell.

Plasma Tendril. Melee Attack: +6 to hit, reach 10 ft., one target. Hit: 14 (2d6 + 7) radiant damage and 4 (1d6) bludgeoning damage.

Teleportation Beam. Creatures in a 120ft long cylinder with a 10ft radius originating from under the Void Jellyfish must make a DC 17 Charisma saving throw. On a failed save, creatures are transported to a different plane of the Void Jellyfish's choosing or its own personal Demiplane. 

A creature can only leave the Void Jellyfish's Demiplane only by using magic that enables planar travel. The Demiplane resembles a location of the Jellyfish's choice roughly 1000ft in diameter and a ceiling of 100ft high. It contains any object or creature transported in this manner. 

The Void Jellyfish can't be harmed from within the Demiplane. If the Jellyfish dies, the Demiplane disappears and everything inside it appears within 5ft of the corpse. The Demiplane is otherwise indestructible.  

Objects of the Jellyfish's choice that are fully enclosed within this beam are automatically transported. 

Dimension Shift. The Void Jellyfish can use its bonus action to teleport to a spot it can see within 60ft of itself. 

Reality Phase. When the Void Jellyfish is targeted by an attack or spell effect, it can use its reaction to phase into another plane, becoming immune to all damage until the end of the attacker's turn.